Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$103.46	5.712%	$109.3696	$109.37	$109.35	$109.40
Purchase #2	$80.82	9.472%	$88.4753	$88.48	$88.50	$88.50
Purchase #3	$36.83	11.286%	$40.9866	$40.99	$41.00	$41.00
Purchase #4	$105.53	6.108%	$111.9758	$111.98	$112.00	$112.00
Purchase #5	$67.63	6.504%	$72.0287	$72.03	$72.05	$72.00
Purchase #6	$43.75	10.524%	$48.3543	$48.35	$48.35	$48.40
Purchase #7	$195.55	4.526%	$204.4006	$204.40	$204.40	$204.40
7 purchase totals =	$633.57		$675.5909	$675.60	$675.65	$675.70